Motor



F. C. HOLTZ Feb. 18, 1930.

MOTOR Filed May 25. 1929 Patented .F eb. 18, 1930 UNITED STATES PATENT oFFicE :rnEnEmCx C. noL'rz, or SPRINGFIELD, ILLINOIS, AssIGNoa 'ro shimano ELECTRIC F SPRINGFIELD, ILLmOIS,

A CORPORATION 0F ILLINOIS IGTOB Application med lay 25, 1929. Serial No. 885,857.: E

This invention relates'to alternating'current electric motors, and more particularly to motors of the reaction type.

One ofthe main objects of my invention is to provide `a relatively small synchronous motor of the reaction type particularly adapted for driving the mechanism of clocks, demand registers, or similar devices. A further object is to provide a motor of this type of comparatively simple and'inexpensife construction, which is rugged and compact, has low synchronous speeds, and in which the torque per watt in-put is high. Another object is to provide a motor of this character in which the stresses in the rotor are balanced, thus eliminating noise due to vibration and producing a motor which is noiseless, or practically so, in its operation, a necessary characteristic of motors to be used for winding clocks and like purposes.

Further objects and advantages of my inyention will appear from the detail description. 1n the drawings:

structed in accordance with my invention;

Figure 2 is a vertical sectional view throughthe motor in the lane of the axis thereof, parts being shown 1n elevation on an enlarged scscale;

Figure 3 is a section taken substantially on linc 3- 3 of Figure 2, the rotor being partly broken away;

1 Figure 4 is a detail edge view, partly in a5* section, of a modifiedform of rotor;

Figure 5 is an outer face view, partly broken away, l,of a modified form o stator.

A motor constructed in accordance with my invention comprises a'cylindrical stator, a coil within the stator, the stator being provided with an annular air ga in the magnetic circuit thereof, and a rotor aving magnetic elements projecting into the air ga In the particular construction illustra by way of example, I provide a tubular core 1 of magnetic material, such as softiron or highly magnetic steel. This core is reduced at one end to provide a neck 2 and a shoulder 3 at the inner endthereof. .A cup shaped casing 4, which is also of vmagnetic material, such Figure 1 is a side view oa motor con-` as soft iron or highly magnetic steel, has its head 5 fitted upon the neck 2 and seating upon shoulder 3. Flange or bodv 6 of this casing is concentric with core l and extends toward the other end thereo.

The core isreduced at its other end to pro` vide a neck 7 4upon the core.

A plate 11, preferably of af non-magnetic material, such as brass, is disposed about neck 2 of the core at the outer face of head 5 oiz casing 4. The outer end of neck 2 is turned over to provide a bead 12 which coacts with shoulder 3 for tightly securing the plate 11 and head 5 on the core. If desired, neck 2 may be exteriory threaded, head 5 and plate 11 eing screwe onto this neck the outer end of which is then rolled over to provide the head 12. It is 'not essential, however, that the plate and the head of the casing be screwed onto neck 2 lwhich may be threaded or not, as desired, land dependmgupon condition. ll also contemplate threading neck 7 and screwin disc 8 onto this neck, if this seems desirs le at any time.

A. plate 13, similar to plate 11, adjacent the outer face of an appreciable distance is disposed. disc 8, but spaced therefrom. The

plates 11 and 13 are secured together by means of screws 14 which pass through ears 15 of the Elate and screw into the ends of spacing memrs or pillars 16 having reduced terminal elements 17 which fit into openings punched in ears 15. Plate' 13 is provided with an outwardly projecting and outwardly tapering central element 18 having at its outer end a flange 19 which tits into a oove in a huh 20 provided at the inner enrof a supporting sleeve 21, ifiange 19 being swedged into the groove of hub 20.

Prior to' securing disc 8 upon neck 7 of core 1, coil 22 is laced about the core and within casing 6. is coil ts tightly about corel and is tightly clamped between head 5 and 8 which is formed of highly magnetic matethe interior diameter of casing 4, delines with the adjacent edge portion of body 6 of thel casing, an annular air gap 23 which is concentric with casing 4. I thus provide a cylindrical stator within which the coil is disposed, this stator having an annular air gap defined by the adjacent edge portions of casing 4 and disc 8', such portion constituting the terminal elements of the metal portion of the path of flow of the ma netic flux of the coil.

The inner e ge portion of body "6 of casing 4 is serrated to provide a plurality of projecting elements, in the form of teeth 24. The slotsseparating these teeth preferably correspond in width to the'width of the teeth and the depth of these slots is somewhat greater than the width of the teeth. Disc 8 'is also provided, at its periphery, with a pluralit of teeth 25 which preferably correspon '1n width and spacing to the teeth 24 of casing 4. There may be considerable variation in the number as wellas size and s acing of the teeth either -on the casing or ont e dise, and it is not essential that both the'disc and the casing be serrated or toothed, as one only of these members need be toothed. I have found, however, that very satisfactory results are ohtained by providing both the casing and the disc 8 with an e ual number 'of teeth whichl correspond inwi th and spacing.

Core 1 is of tubular construction, the bore thereof being of step ed formation and decreasing in diameter rom neck 12. A bearingv ring 26 is mounted in the intermedi-ate lportion of the bore of core Yl and is secured against axial movement therein by a screw p ug 27 screwed into the largest portion of the bore of core 1, through neck 2. Sleeve 21 has the `outer end portion of its bore of stepped formation and receives a'bearingring 28 secured in position between an interior shoulder in the sleeve and a screw plug 29 which screws into the outer end of the sleeve. A rotor shaft 30 is rotatably mounted in the bearing, collars 26 and 28 by means of'reduced end trunnions 31. A pinion 32 is secured on shaft 30 and 'is adapted for mesh with a gear to be driven thereby, sleeve 31 being provided with a slot 33 to accommodate such a gear.

' A rotor 34 is secured on shaft 30 in any suit- I able manner, as by being pressed thereon. This rotor comprises a disc 35 formed of a suitable non-magnetic material. A kplurality of pins 36 are securedin the disc 34 and project inwardly therefrom .into the air gap 23. These pins preferablycorrespond in number and spacing to the teeth of disc 8 and casing 4, though this is not'essential as the number of pins can be varied within wide limits. The speed of the rotor, in R. P. M. is determined bythe formula S '-1 1.20%| wherelF is the `freojuency. of the alternating current supply and possible to remove any number of the pins of the rotor, down to the last pi n, without altering the formula. Bymaking the number of pins in the rotor less than and prime to the number of'cooperating pairs o f stator projections the speed of the rotor may be reduced. Inthis case the formula becomes where R is the number of pins in the rotor prime to P. While such construction is conducive to quite lowspeed, a motor in` which the number of pins inthe rotor is apprec iably less than the. number of stator polar projections is generally less quiet in operationthan when the pins in the rotor are equal in number to the'cooperating pairs ofstator polar projections. This islprobably due to some slight 4ina'ccuracy'in balance of the ro-' tor. By employing a greater number of pins, the vibrations due to any inaccuracy in balance of the rotor is greatly reduced or eliminated With the result that the motor is practically noiseless in operation. A further advantage of employing the same number of pins in the rotor as there are pairs of polar projections in the stator is that this construction-results in higher torque than is possible w'ith any other combination of pins and polar projections. By my construction above set Orth, render itpossi-ble to provide a large number of ples within a comparatively small space, which giveshigh torque and low synchronous speed, which are desirable characteristics of motors of this type. 4

In the particular motor illustrated, I employ l18\-poles, thatis, 48 teeth or projectionsv on casing 4 and on disc 8 and use 48 pins on ilo the stator which, with a 60 cycle alternating v current gives la speed of 150 R. P. M.\ in accgrdance with the above stated formula.

dh'e pin's 36 of the rotor are disclosed as spacedan appreciable distance from the teeth y of the casingand the teeth ofthe disc 8. In "practice the diameter of the ins should be such as to practically span t e air gap between the aligned projections or teeth of casing 4 and discs 8, only such clearance being provided as is essential for mechanical considerations. In the operation of the motor, when coil 22 is connected into an alternating 'current circuit, by means of the leads 22 provided for this purpose, a ma neticl circuit is set up through the stator, thls circult including the air gap 23. The relatively great reluctance of this air gap to owof the :se pins 36 o magnetic flux is an important feature in the operation of the motor. This motor is not self-starting and it is necessary, therefore, to turn the rotor by hand when starting the motor. When the pins 36 are disposed in alignment with the spaces 24a and 25 between the teeth 24 and 25 of casing 4 and discs 8, respectively, the reluctance of the magnetic circuit of the stator is a maximum. As the pins approach alignment with the pairs of teeth or polar projections vof the disc 8 and casing 4, the .reluctance of' the air gap decreases, and when the coil 22 is energized serves to pull the rotor in the direction in which the pins 36 are effected by the magnetic flux. l

The motor operates in accordance with the known theory of reaction motors, and when the rotor is brought up to its proper operating speed in accordancejwith the above stated formula, it will lock into step with therotating fields created, and will thereafter run synchronously with 'considerable torque. In Figure 4, I have illustrated a modified formof rotor. This form comprises a disc 37 of a suitable non-magnetic material into which is set a collar 38 of a magnetic material, the inner edge of this collar being serrated to rovide teeth 39 corresponding to fp the rotor of F igres 2 and 3. The disc 37 may convenientlybe formedjof a condensation product molded into shape, such disc beinv molded about the collar 38. The disc mayrbe secured on the rotor shafty in any suitable manner, as by being molded thereon, or secured thereto by any other known means. A rotor constructed in this manner operates in the same manner as the rotor of Figures 2 and 3, the rotor being so disposed that the teethv 39 thereof extend into the air gap A23. j The motor illustrated in Figures 1,2, and 3 is not self-starting. This motor can be rendered self-starting, however, by providing aidisc 40. of Y a non-magnetic material (Fig. 5) and which is a good conductor of electricity, disposed between an inner disc 41 and an outerldisc 42 secured on neck 7 of the core, these discs replacing the discs 8 of Figure 2. Discs 41 and 42 are formed of magnetic material, and are toothed in the sume manner as discs 8, the teeth of the outer disc 42 being disposed slightly inadvance of tlie teeth of thejinner disc 41 in relation to the direction of rotation of the rotor, it being considered in this figure that the rotor turns in a clockwise direction.

When the circuit through coil 22 is closed, Foucaultoreddy currents are set up in the copper disc 40 and create a strong shifting magnetic field in the annular air gap 23, it being understood that the discs 41 and 42 are disposed in the same relation to the adjacent end of body 6 of casing 4, as disc 8 in Figure 2. This shifting magnetic field is closely analogous to a rotating magnetic field and acts upon the elements ofthe rotor which project into the air gap in such manner as to cause rotation thereof under sufficient torque to bringthe rotor up to proper speed where it will lock magnetically `into step and run synchronously. By reversing the relation between thc teeth of the discs 41 and 42, that is, b disposing the teeth of disc 42 in advance of t e teeth of disc 41, in the opposite direction to that illustrated in Figure 5, fhe'direction of rotation of the rotor will be reversed in accordance with well established principles. In self-starting motors the teeth of projections of the casing 4 may be made of less depth or, in some instances, may be entirely dispensed with.

What I claim is:

1. In an electric motor of the character described, ajstator comprising a core and a cupshaped casing secured to the core and having close magnetic coupling therewith, the core and the casing being of `magnetic material, a coil disposed about the core and within the casing with one ,end adjacent the casing head, a disc of magnetic material disposed adjacent the other end of the casing and spaced therefrom, said disc having close magnetic coupling with the core, the disc having spaced projections extending toward the casing and spaced therefrom, said projections and the adjacent end of the casing defining an annular air gap, anda rotor c omprisinga nonmagnetic support and a plurality of magnetic elements carried thereby and projecting into said air' gap.

2. In an electric motor of the character described, a substantially cylindrical stator of magnetic material comprising a core and end heads closely coupled magnetically to the core, said stator having an air gap therein concentric with the core and being provided with spaced elements disposed adjacent and substantially in the plane of the air gap, a coil disposed within the stator,-and a rotor comprising a non-magnetic support and a lurality of mangetic elements carried there y and projecting into said air gap. Y

3. In an electrlc motor of the character described, a stator comprising a core, a cup shaped casingsecured thereon at one end, said core and casing being of magnetic material, a disc of magnetic material secured on the core at the other end of the casing and spaced therefrom, the disc and the adjacent end of the casing defining an annular air gap, the stator having spaced elements disposed substantially in the plane of said gap, a coil disposed about the core and within the casing, and a rotor comprising a non-magnetic support and a plurality of magnetic elements carried thereby and projecting into the air gap.

4. In an electric motor of the character described, a substantially cylindrical stator of magnetic material comprising a body and vof magnetic material secure end heads magnetically coupled thereto, said stator having a concentric air gap and being provided with spaced elements disposed adjacent and substantially in the plane of the air gap, a coil disposed Within the the stator and having magnetic coupling therewith and a rotor comprising a non-magnetic support and a plurality of magnetic elements Acarried thereby and projecting into said air gap.

5. In an electric motor of the character ,described, a magnetic core, a cu shaped casing on the core, a disc of magnetic material secured on the core and disposed within the open endof the casing .in concentric spaced relation thereto, a coil mounted about the core and within the casing, the adjacent terminal elements of the metallic path of ilow of the magnetic fiux through the stator structure defining, an annular air gap, one of said elements being provided with spaced projections disposed substantially in the plane o t said gap, and a rotor comprising a non-magnetic support and a plurality of magnetic elements carried thereby and projecting into said air gap.

6. In an electric motor of the character-'described, a magnetic core, a cup shaped casing secured on said core, said casing being of magnetic material, a disc of magnetic material secured on the core within theopen end of the casing and in concentrick spaced relation thereto, a coil mounted about the core and within the casing, the periphery ot the disc being toothed and the adjacent edge portion of the' casing being similarly toothed, and a rotor comprising a non-magnetic support'and a plurality of magnetic elements carried thereby and projecting between the disc and the adjacent `edge portion of the casing.

7. In an electric motor of the character described, a frame comprising front and back plates secured together in spaced relation, a core of magnetic material secured to 'the back plate, a cup shaped casing of magnetic material secured about the core and between the same and the back plate, a disc of magnetic material secured on the core within the open end of the casing and in concentric relation thereto, said disc being ot less diameter than the interior diameter of the casing and defining with the adjacent edge portion thereof an annular air gap, the periphery of the disc being toothed, a supporting sleeve carried by the front plate, a i'otor shaft rotatably mounted in said sleeve and in the core, a coil disposed about said core and within the casing, and arotor secured on said shaft and comprising magnetic elements extending into the air gap.

8. In an electric motor of the character described. a substantially' cylindrical stator of magnetic material comprising a cup shaped casing and a disc mounted at the open end of the casing in spaced relation thereto and definin'g therewith an annular air gap, the disc and the adjacent edge portion of the casing being provided with teeth corresponding in width and spacing, a coil disposed within the stator, anda rotor comprising magnetic elements extending into said air gap.

9. In an electric motor of thc character described, a substantially cylindrical stator of magnetic material comprising a cup shaped casing and a disc disposed within one end of the casing in concentric spaced relation thereto and defining therewith an annular air gap, a coil disposed within the casing between the other end thereof and the disc, the periphery of the disc being serrated to provide a plurality of radially projecting teeth and the adjacent edge of the casing also being serrated to provide a plurality of teeth, the teethy of the disc and the teeth of the casing being similar in width and spacing and disposed in alignment, and a rotor comprising a plurality of magnetic elements projecting into said air gap, the elements of the rotor corresponding in number and spacing to the teeth of the disc.

10. In an electric motor ofthe character described, a rotor comprising a disc of non-magnetic material, and a collar set into the disc and provided with a plurality of axially projecting magnetic elements.

11. In an electric motor of the character described, a rotor comprising a disc of nonmagnetic material, and a collar of magnetic material set into the disc at one side thereof,

'said collar being serrated to provide a plurality of spaced axially projecting magnetic elements.

12. In an electric motor of the character described, a statorl element comprising two discs of magnetic material and a third disc of non-.magnetic material of high electrical conductivity secured between the two magnetic discs.

13. In an electric motor of the character described, a stator element comprising two discs of magnetic material and a third disc of non-magnetic material of high electrical conductivity secured between said two discs, the tWo magnetic discs having their peripheral portions serrated to provide radially Tirojecting teeth.

14. In an electric motor of the character described, a stator elem'ent comprising two outerdiscs of magnetic material and an inner disc of non-magnetic material and high electrical conductivity secured between the outer discs, the outer discs having their peripheral portions serrated to provide spaced radially projecting teeth and the teeth of said outer discs being disposed out of alignment.

In witness whereof. I hereunto subscribe my name this 22 day of May, 19:29.

. FREDERICK C. HOLTZ. 

